Ferroelectric properties and dielectric responses of multiferroic BiFeO₃ films grown by RF magnetron sputtering

Multiferroic BiFeO₃ films have been grown on LaNiO _3-x/SrTiO₃ and Pt/Si substrates by RF magnetron sputtering. The films showed fully saturated ferroelectric hysteresis loops with large remanent polarization of 64 νC cm^-2, suitable for most device applications. Piezoresponse force microscopy confirmed that the films were electrically writable. In addition to the high-frequency intrinsic dielectric loss of epitaxial films, the Argand diagram also revealed low-frequency contributions from both dc conductivity and interfacial polarization at electrodes. For polycrystalline films on Pt/Si, the dominant contribution to dielectric loss was space charge polarization at grain boundaries.